Controls on Thermokarst Lake Water Balances in the Inuvik - Tuktoyaktuk Region

There are tens of thousands of thermokarst lakes in the Inuvik-Tuktoyaktuk region, located in the northwest corner of the Northwest Territories, Canada. These lakes formed following the last glacial period in areas where ice-rich permafrost thawed and created depressions in the landscape. The Inuvik-Tuktoyaktuk region is one of the fastest warming regions in the world, leading to changing precipitation patterns, permafrost thaw and deciduous shrub expansion, all of which are affecting the water balance of thermokarst lakes. During the past several decades, lake expansion and contraction have been observed in response to fluctuations in precipitation. While these changes in lake surface area and number have been documented, less is known about how varying meteorological conditions, lake and landscape features, and hydrological processes have regulated these changes in thermokarst lake water balances. Many studies documenting fluctuations in lake surface area often observe some lakes expanding in area while others contract during the same period of time, suggesting that lake and watershed properties regulate how lakes react to climate change. Rapid lake drainage, which can be initiated by extremely high lake levels, is occurring at an increasing rate. The main objective of this thesis is to quantify the drivers of variability in thermokarst lake water balance components (e.g. inflow, evaporation, lake level, lake water source composition), so that we may better understand how lakes will respond to ongoing climate change. Multiple properties of the environment have the potential to influence thermokarst lake water balances: seasonal and inter-annual variation in meteorological conditions (i.e. air temperature and precipitation), watershed properties (e.g. surface area, vegetation, topography, permafrost), and lake properties (e.g. depth, surface area, outlet channel presence). Achieving the objective of this thesis involves measuring lake water balances and quantifying how the environmental properties described above affect lake water balance components. The four main research chapters of this thesis divide this task into smaller parts, with each chapter quantifying a subset of lake water balance components or environmental conditions at different spatial and temporal scales. The second chapter explores the interaction between snow and shrubs and their ultimate impact on frost table depth, which influences runoff from lake watersheds. Shrubs are expanding across the Arctic and affecting snow depth, snowmelt timing and soil shading, which in turn influences frost table depth. Hummocks, which are mineral-earth domes 0.5 - 1.0 m across formed over hundreds of years via the cyclical freezing and thawing of the uppermost soil layer (active layer), are common features on hillslopes in the Inuvik-Tuktoyaktuk region. Between hummocks lie a mesh-like network of inter-hummock zones that are filled with peat and form a preferential flow network on hillslopes. When hummocks degrade due to permafrost thaw, they collapse and mineral soils invade inter-hummock zones and reduce the hydraulic conductivity. Frost table depth, snow depth and the snow-free date were measured in hummock and inter-hummock zones at the Siksik Creek watershed throughout the summer of 2015 in shrub-covered and shrub-free locations. Areas of birch shrubs had earlier snowmelt dates, and experienced greater hummock frost table depths. In inter-hummock zones, frost table depth was shallower when adjacent hummocks were taller, indicating that inter-hummock frost table depths increase when hummocks collapse. Future birch shrub expansion may accelerate permafrost thaw, leading to hummock collapse and a reduction in the ability of hillslopes to convey runoff. Chapter three focuses on the degree to which freshet runoff mixes with lake water, as the snowmelt period represents the largest volumetric input of water to lakes. Previous studies have observed a phenomenon called snowmelt bypass whereby water flowing into ice-covered lakes flows underneath lake ice and out of the lake without mixing with the entire water column. Snowmelt bypass occurs when the freshet runoff flowing into lakes (approx. 0◦C) is less dense than deeper lake waters (\u3c4◦C), a condition that is typically present at the start of snowmelt runoff; however, lakes generally become more mixed towards the end of the snowmelt period. Using lake water isotope data from before and after the freshet, the percentage of lake water replaced by freshet runoff and the average lake source water isotope composition (I) was quantified for seventeen lakes and compared to lake and watershed properties. Lake depth significantly influenced the amount of lake water replaced by freshet runoff, with deeper lakes retaining less freshet runoff because a larger portion of the lake volume was isolated from mixing with freshet runoff. Additionally, isotope data showed that the source of freshet runoff remaining in lakes contained a mixture of snow-sourced and soil-sourced water. The snowmelt bypass effect was likely stronger earlier in the freshet when runoff was more snow-sourced, while later in the freshet when runoff was likely more soil water-sourced, stronger vertical mixing in the lake was likely present and the snowmelt bypass effect would have been weaker. Earlier snowmelt relative to lake-ice melt caused by shrubification could lead to greater snowmelt bypass in the future, with the freshet runoff remaining in lakes becoming even more soil water-sourced. A shift to more soil-sourced freshet may impact lake chemistry, as soil-sourced runoff has lower concentrations of dissolved organic carbon, lower conductivity and higher pH than snow-sourced runoff. These results are relevant for open-drainage lakes, which can experience snowmelt bypass since any excess water is able to flow through the lake outlet. The fourth chapter investigates how lake and watershed properties mediate the response of lakes to seasonal shifts in meteorological conditions using an isotope hydrology approach. Twenty-five lakes along the Inuvik-Tuktoyaktuk Highway were water sampled five times during 2018 for isotope analysis, with sampling starting before snowmelt and ending in early September. Lake water isotope compositions were used to estimate the ratio of evaporation-to-inflow (E/I) and (I). Four distinct seasonal phases of lake water balance were identified from the isotope data and prevailing meteorological conditions. The initial Freshet Phase occurred during snowmelt, with lakes experiencing a reduction in E/I and shift in I towards the average isotope composition of precipitation. An Evaporation Phase followed, a period of typically warm air temperatures and minimal precipitation, during which E/I increased and I remained stable due to minimal inflow. As air temperatures declined and precipitation increased, the Soil Wetting Phase began, where E/I and I did not respond to initial rainfall as dry soils had not yet reached a moisture level sufficient to generate runoff. As rainfall persisted and soils become wetter, the Recharge Phase initiated, during which E/I declined and I became more rain-like as inflow to lakes increased and evaporation decreased as solar radiation and air temperature declined. Variability in E/I among lakes was strongly correlated with the ratio of watershed area to lake area (WA/LA), where lakes with smaller WA/LA had larger E/I ratios because they received less inflow relative to evaporation. The majority of lakes in the region have a WA/LA Chapter five analyzes year-to-year differences in lake water balance components for a single lake in the region. Three years of lake water balance measurements were made at Big Bear Lake near the Trail Valley Creek research station. The water balance was calculated daily between May 1 and October 30, such that ΔLL = P + Qin - Qout - E, where LL is lake level, P is precipitation, Qin is inflow, Qout is outflow, and E is evaporation. Lake level was measured using a pressure transducer type water level recorder and outflow was estimated using a stage-discharge relationship derived from manual discharge measurements made at the lake outlet. Evaporation was estimated using the Priestley-Taylor method, while precipitation was measured using a shielded weighing gauge. Inflow was calculated as the unknown variable in the lake water balance equation, but was set to 0 if the estimated inflow was a negative value. During the freshet period, the runoff ratio (i.e. the percentage of snowpack and precipitation converted into inflow) was highest when the snowmelt occurred rapidly or when the previous year experienced higher levels of summertime precipitation. Rapid snowmelt also caused higher maximum lake levels at the time of snow dam failure. Summertime runoff ratios were higher in wetter years, but were also affected by the previous year’s summertime precipitation, with higher runoff ratios when the preceding year was wetter. Evaporation losses varied between 226 to 296 mm, with the length of the ice-free period largely controlling the amount of evaporation that occurred. There was a large potential for evaporation (4 to 6 mm day-1) in the days leading up to the lake becoming ice-free, implying that the ice-free date has a strong impact on total evaporative losses from lakes. Predicting whether lake water balances become wetter or drier in the future requires understanding how increasing active layer depths, degrading hummocks and shrub expansion will affect runoff ratios under predicted wetter summers, while ice-free seasons lengthen and lake evaporative losses increase. Overall, this thesis improves our understanding of the controls on thermokarst lake water balances in the western Canadian Arctic. Specifically, this thesis outlines the strong predictive power of lake and watershed attributes in describing variability in lake water balances, a concept that could be further developed by integrating more variables from remote sensing data and more advanced statistical methods to quantify the influence of less influential lake and landscape attributes on lake water balance. This thesis also advances our understanding of the freshet period, including the influence of different shrub species on snow depth, snowmelt timing and frost table depth, the drivers of lake level maximums and snow dam failure, and the impact of lake depth on the mixing of snow- and soil-sourced water into ice-covered lakes. The complexity of interactions between climate change and spatially variable landscape elements make it difficult to foresee whether lakes will experience a wetter or a drier future water balance, as climate-induced changes may increase runoff (e.g. more rainfall, wetter soils and increased runoff ratios), or decrease runoff (e.g. shrub expansion, greater rainfall interception, drier soils and decreased runoff ratios), which will either offset or amplify increases in lake evaporation losses. Given our observations of increasing E/I ratios with decreasing WA/LA in Chapter 4, we may expect under drier future conditions that lakes with smaller WA/LA are the first to decrease in surface area, while under wetter conditions lakes with larger WA/LA may be more vulnerable to rapid drainage as they experience greater increases in lake level. These hypotheses could be tested with multi-decadal remote sensing time series and observing how the lake surface area of lakes with different WA/LA behave during wetter and drier periods. Future scenarios for lake water balances may also be investigated with hydrological models, as the capability of models for representing relevant cold-regions processes such as snow redistribution and ground subsidence after permafrost thaw is improving

Visual perception of photographs of rotated 3D objects in goldfish (Carassius auratus)

© The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Wegman, J. J., Morrison, E., Wilcox, K. T., & DeLong, C. M. Visual perception of photographs of rotated 3D objects in goldfish (Carassius auratus). Animals, 12(14), (2022): 1797, https://doi.org/10.3390/ani12141797.This study examined goldfishes’ ability to recognize photographs of rotated 3D objects. Six goldfish were presented with color photographs of a plastic model turtle and frog at 0° in a two-alternative forced-choice task. Fish were tested with stimuli at 0°, 90°, 180°, and 270° rotated in the picture plane and two depth planes. All six fish performed significantly above chance at all orientations in the three rotation planes tested. There was no significant difference in performance as a function of aspect angle, which supported viewpoint independence. However, fish were significantly faster at 180° than at +/−90°, so there is also evidence for viewpoint-dependent representations. These fish subjects performed worse overall in the current study with 2D color photographs (M = 88.0%) than they did in our previous study with 3D versions of the same turtle and frog stimuli (M = 92.6%), although they performed significantly better than goldfish in our two past studies presented with black and white 2D stimuli (M = 67.6% and 69.0%). The fish may have relied on color as a salient cue. This study was a first attempt at examining picture-object recognition in fish. More work is needed to determine the conditions under which fish succeed at object constancy tasks, as well as whether they are capable of perceiving photographs as representations of real-world objectsThis work was supported with a RIT College of Liberal Arts Faculty Development Grant to CMD and the RIT Paul A. and Francena L. Miller Research Fellowship awarded to CMD from the Rochester Institute of Technology

Linking tundra vegetation, snow, soil temperature, and permafrost

Connections between vegetation and soil thermal dynamics are critical for estimating the vulnerability of permafrost to thaw with continued climate warming and vegetation changes. The interplay of complex biophysical processes results in a highly heterogeneous soil temperature distribution on small spatial scales. Moreover, the link between topsoil temperature and active layer thickness remains poorly constrained. Sixty-eight temperature loggers were installed at 1-3 cm depth to record the distribution of topsoil temperatures at the Trail Valley Creek study site in the northwestern Canadian Arctic. The measurements were distributed across six different vegetation types characteristic for this landscape. Two years of topsoil temperature data were analysed statistically to identify temporal and spatial characteristics and their relationship to vegetation, snow cover, and active layer thickness. The mean annual topsoil temperature varied between -3.7 and 0.1°C within 0.5 km2. The observed variation can, to a large degree, be explained by variation in snow cover. Differences in snow depth are strongly related with vegetation type and show complex associations with late-summer thaw depth. While cold winter soil temperature is associated with deep active layers in the following summer for lichen and dwarf shrub tundra, we observed the opposite beneath tall shrubs and tussocks. In contrast to winter observations, summer topsoil temperature is similar below all vegetation types with an average summer topsoil temperature difference of less than 1°C. Moreover, there is no significant relationship between summer soil temperature or cumulative positive degree days and active layer thickness. Altogether, our results demonstrate the high spatial variability of topsoil temperature and active layer thickness even within specific vegetation types. Given that vegetation type defines the direction of the relationship between topsoil temperature and active layer thickness in winter and summer, estimates of permafrost vulnerability based on remote sensing or model results will need to incorporate complex local feedback mechanisms of vegetation change and permafrost thaw

Arctic soil methane sink increases with drier conditions and higher ecosystem respiration

Arctic wetlands are known methane (CH4) emitters but recent studies suggest that the Arctic CH4 sink strength may be underestimated. Here we explore the capacity of well-drained Arctic soils to consume atmospheric CH4 using >40,000 hourly flux observations and spatially distributed flux measurements from 4 sites and 14 surface types. While consumption of atmospheric CH4 occurred at all sites at rates of 0.092 ± 0.011 mgCH4 m−2 h−1 (mean ± s.e.), CH4 uptake displayed distinct diel and seasonal patterns reflecting ecosystem respiration. Combining in situ flux data with laboratory investigations and a machine learning approach, we find biotic drivers to be highly important. Soil moisture outweighed temperature as an abiotic control and higher CH4 uptake was linked to increased availability of labile carbon. Our findings imply that soil drying and enhanced nutrient supply will promote CH4 uptake by Arctic soils, providing a negative feedback to global climate change

The validation of pharmacogenetics for the identification of Fabry patients to be treated with migalastat

PURPOSE: Fabry disease is an X-linked lysosomal storage disorder caused by mutations in the α-galactosidase A gene. Migalastat, a pharmacological chaperone, binds to specific mutant forms of α-galactosidase A to restore lysosomal activity. METHODS: A pharmacogenetic assay was used to identify the α-galactosidase A mutant forms amenable to migalastat. Six hundred Fabry disease-causing mutations were expressed in HEK-293 (HEK) cells; increases in α-galactosidase A activity were measured by a good laboratory practice (GLP)-validated assay (GLP HEK/Migalastat Amenability Assay). The predictive value of the assay was assessed based on pharmacodynamic responses to migalastat in phase II and III clinical studies. RESULTS: Comparison of the GLP HEK assay results in in vivo white blood cell α-galactosidase A responses to migalastat in male patients showed high sensitivity, specificity, and positive and negative predictive values (≥0.875). GLP HEK assay results were also predictive of decreases in kidney globotriaosylceramide in males and plasma globotriaosylsphingosine in males and females. The clinical study subset of amenable mutations (n = 51) was representative of all 268 amenable mutations identified by the GLP HEK assay. CONCLUSION: The GLP HEK assay is a clinically validated method of identifying male and female Fabry patients for treatment with migalastat

The National COVID Cohort Collaborative (N3C): Rationale, design, infrastructure, and deployment.

OBJECTIVE: Coronavirus disease 2019 (COVID-19) poses societal challenges that require expeditious data and knowledge sharing. Though organizational clinical data are abundant, these are largely inaccessible to outside researchers. Statistical, machine learning, and causal analyses are most successful with large-scale data beyond what is available in any given organization. Here, we introduce the National COVID Cohort Collaborative (N3C), an open science community focused on analyzing patient-level data from many centers. MATERIALS AND METHODS: The Clinical and Translational Science Award Program and scientific community created N3C to overcome technical, regulatory, policy, and governance barriers to sharing and harmonizing individual-level clinical data. We developed solutions to extract, aggregate, and harmonize data across organizations and data models, and created a secure data enclave to enable efficient, transparent, and reproducible collaborative analytics. RESULTS: Organized in inclusive workstreams, we created legal agreements and governance for organizations and researchers; data extraction scripts to identify and ingest positive, negative, and possible COVID-19 cases; a data quality assurance and harmonization pipeline to create a single harmonized dataset; population of the secure data enclave with data, machine learning, and statistical analytics tools; dissemination mechanisms; and a synthetic data pilot to democratize data access. CONCLUSIONS: The N3C has demonstrated that a multisite collaborative learning health network can overcome barriers to rapidly build a scalable infrastructure incorporating multiorganizational clinical data for COVID-19 analytics. We expect this effort to save lives by enabling rapid collaboration among clinicians, researchers, and data scientists to identify treatments and specialized care and thereby reduce the immediate and long-term impacts of COVID-19

Lattice QCD and Particle Physics

Contribution from the USQCD Collaboration to the Proceedings of the US Community Study on the Future of Particle Physics (Snowmass 2021).Comment: 27 pp. main text, 4 pp. appendices, 30 pp. reference

SpHincterotomy for Acute Recurrent Pancreatitis Randomized Trial: Rationale, Methodology, and Potential Implications

Objectives: In patients with acute recurrent pancreatitis (ARP), pancreas divisum, and no other etiologic factors, endoscopic retrograde cholangiopancreatography (ERCP) with minor papilla endoscopic sphincterotomy (miES) is often performed to enlarge the minor papillary orifice, based on limited data. The aims of this study are to describe the rationale and methodology of a sham-controlled clinical trial designed to test the hypothesis that miES reduces the risk of acute pancreatitis. Methods: The SpHincterotomy for Acute Recurrent Pancreatitis (SHARP) trial is a multicenter, international, sham-controlled, randomized trial comparing endoscopic ultrasound + ERCP with miES vs. endoscopic ultrasound + sham for the management of ARP. A total of 234 consented patients having two or more discrete episodes of acute pancreatitis, pancreas divisum confirmed by magnetic resonance cholangiopancreatography, and no other clear etiology for acute pancreatitis will be randomized. Both cohorts will be followed for a minimum of 6 months and maximum of 48 months. Results: The trial is powered to detect a 33% risk reduction of acute pancreatitis frequency. Conclusions: The SHARP trial will determine whether ERCP with miES benefits patients with idiopathic ARP and pancreas divisum. Trial planning has informed the importance of blinded outcome assessors and long-term follow-up

Lattice QCD and Particle Physics

Contribution from the USQCD Collaboration to the Proceedings of the US Community Study on the Future of Particle Physics (Snowmass 2021)

Effects of Anacetrapib in Patients with Atherosclerotic Vascular Disease

BACKGROUND: Patients with atherosclerotic vascular disease remain at high risk for cardiovascular events despite effective statin-based treatment of low-density lipoprotein (LDL) cholesterol levels. The inhibition of cholesteryl ester transfer protein (CETP) by anacetrapib reduces LDL cholesterol levels and increases high-density lipoprotein (HDL) cholesterol levels. However, trials of other CETP inhibitors have shown neutral or adverse effects on cardiovascular outcomes. METHODS: We conducted a randomized, double-blind, placebo-controlled trial involving 30,449 adults with atherosclerotic vascular disease who were receiving intensive atorvastatin therapy and who had a mean LDL cholesterol level of 61 mg per deciliter (1.58 mmol per liter), a mean non-HDL cholesterol level of 92 mg per deciliter (2.38 mmol per liter), and a mean HDL cholesterol level of 40 mg per deciliter (1.03 mmol per liter). The patients were assigned to receive either 100 mg of anacetrapib once daily (15,225 patients) or matching placebo (15,224 patients). The primary outcome was the first major coronary event, a composite of coronary death, myocardial infarction, or coronary revascularization. RESULTS: During the median follow-up period of 4.1 years, the primary outcome occurred in significantly fewer patients in the anacetrapib group than in the placebo group (1640 of 15,225 patients [10.8%] vs. 1803 of 15,224 patients [11.8%]; rate ratio, 0.91; 95% confidence interval, 0.85 to 0.97; P=0.004). The relative difference in risk was similar across multiple prespecified subgroups. At the trial midpoint, the mean level of HDL cholesterol was higher by 43 mg per deciliter (1.12 mmol per liter) in the anacetrapib group than in the placebo group (a relative difference of 104%), and the mean level of non-HDL cholesterol was lower by 17 mg per deciliter (0.44 mmol per liter), a relative difference of -18%. There were no significant between-group differences in the risk of death, cancer, or other serious adverse events. CONCLUSIONS: Among patients with atherosclerotic vascular disease who were receiving intensive statin therapy, the use of anacetrapib resulted in a lower incidence of major coronary events than the use of placebo. (Funded by Merck and others; Current Controlled Trials number, ISRCTN48678192 ; ClinicalTrials.gov number, NCT01252953 ; and EudraCT number, 2010-023467-18 .)